Bacteremia caused by a lactose-fermenting, multiply resistant Salmonella typhi strain in a patient recovering from typhoid fever.

A female patient suffered a typical attack of typhoid fever due to a lactose-negative, fully susceptible Salmonella typhi strain. During convalescence she became febrile, and a lactose-fermenting S. typhi strain resistant to ampicillin, chloramphenicol, tetracycline, and trimethoprim was isolated from blood culture. This isolated was shown to harbor a plasmid which cotransferred lactose fermentation and antibiotic resistance.